What is it like to run out of juice?

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Joined
May 18, 2015
Messages
8
I've never allowed my iMiev to get even close to a dead battery. I generally fill it up after about 50 miles. As such, I have a few questions:

* Have you ever run out of power? How did the car behave?
* Does the car change how it behaves as the battery gets low? (like a flash light getting dimmer)
* Does the power-meter work roughly like a gas gauge? ie: can you can generally get another 10 miles after it hits zero?

-Alex


ps: I'm sure someone else has asked this question so I tried searching for this in the forum. Unfortunatly I kept getting a message that my search words were too common. PHPbb is not known for its fantastic search system.
 
I have no personal experience of this, either, but supposedly the car switches to "turtle mode" before it runs out. Searching that term should be more effective. (Also, don't forget, you can use Google to search a specific site, e.g., "site:myimiev.com turtle".)
 
https://www.google.com/search?q=site%3Amyimiev.com+turtle&ie=utf-8&oe=utf-8

This is what Google came up with, I didn't look ... yet.

I do know that mine blinks (gas can and bars) at 2 bars and at One bar. I have not hit Turtle mode yet
 
Those cell voltages are all over the place--i would have thought or expected a more level draw-down where all the cells were about the same.

What do you suppose causes the cell voltage variation?
 
I think you're just seeing the nature of the beast. In general, Lithium cells have a very flat discharge curve, ie: their voltage remains steady until the charge is nearly exhausted, and then the voltage falls rapidly. This is when any capacity or state-of-charge imbalances withing a pack will show themselves, and the reason that a faction of the EV hobbyist community passionately believes in 'bottom balancing' for battery management.
Here's a discharge curve for our cells, originally posted by another poster... You'll see that Malm's cells, at 3.5 to 3.25 V are not even into the knee of the curve yet, and further discharge down to 2.75V is when things would really get interesting...
https://flic.kr/p/pCJhnP
 


Min = 2,755 V Avg = 2,974 V Max = 3,290 V

The car is in a real 0,0% SoC in this situation (weakest cell at 2,75 V). It stopped with one bar, without going to turtle mode. The car did that in the past, don't do it anymore. Now each bar is less energy that in that time (do less miles with each bar), but stop at 0,0% SoC with weakest cell over 2,75 V (but not by much).
 
logicalmethods said:
I've never allowed my iMiev to get even close to a dead battery. I generally fill it up after about 50 miles. As such, I have a few questions:
* Have you ever run out of power? How did the car behave?
* Does the car change how it behaves as the battery gets low? (like a flash light getting dimmer)
* Does the power-meter work roughly like a gas gauge? ie: can you can generally get another 10 miles after it hits zero?
In almost 50,000 total i-MiEV miles we've never seen turtle.

The car will have reduced power before it actually stops dead, so you will have plenty of warning. If you need to keep going as you approach zero bars and below, be VERY DELICATE with your accelerator pedal.

The "power-meter" is, strictly speaking, an "Energy meter". When the car was brand-new, you might have conceivably gone another ten miles - there's a video of a ditzy reporter who did just that if you look through some of the 2012 reviews or videos; however, as the car ages as best we can tell the usable battery capacity is removed from the bottom and thus the turtle range diminishes. Don't count on it!

Best to simply avoid the possibility of going to zero bars, that's all.
 
I agree with JoeS, most of us don't really know how much miles our turtle last. Without Canion, we will not have a clue of the moment of stopping. I know that my car, in these days, allow me to use 9,5% SoC in turtle mode, but I know this because sometimes (twice an year) I discharge the car to 0,0% SoC. Not advise anyone to do the same, because going to low voltages is not the best thing to do to make our batteries last.
 
I've got a canion .db file of my i running out of charge. If anyone can help me with instructions on plotting the data I can post it here.

Pete
 
Howdy Malm,

if i look at your canion screens, it appears that 14.5% SOC at 50,784 km had cells at H:3.290 L:2.755,

but later at 63,461 km it showed 0.0% SOC with cells at H:3.505 L:3.250.

i'm puzzled that the lower voltage cells indicated a higher SOC, and the higher voltage cells indicated lower SOC?

Is this typical or some artifact of the onboard sensors, or canion app, etc.? This data seems contrary to what i would be expecting with respect to voltage and SOC.

Any explanations would be welcome here to help understand what's happening. Thanks, kenny
 
kiev said:
Howdy Malm,

if i look at your canion screens, it appears that 14.5% SOC at 50,784 km had cells at H:3.290 L:2.755,

but later at 63,461 km it showed 0.0% SOC with cells at H:3.505 L:3.250.

i'm puzzled that the lower voltage cells indicated a higher SOC, and the higher voltage cells indicated lower SOC?

Is this typical or some artifact of the onboard sensors, or canion app, etc.? This data seems contrary to what i would be expecting with respect to voltage and SOC.

Any explanations would be welcome here to help understand what's happening. Thanks, kenny

That is simple for me to explain. Between the two moments, my car made a calibration of the capacity. In the first one, 100% SoC was equal to something like 15/16 kWh in the battery. In the second, 100% SoC is something like 13 kWh. So 100% SoC is less energy now and that's why it stops with higher voltages.
 
logicalmethods said:
* Have you ever run out of power? How did the car behave?
* Does the car change how it behaves as the battery gets low? (like a flash light getting dimmer)
* Does the power-meter work roughly like a gas gauge? ie: can you can generally get another 10 miles after it hits zero?

I have never fully run out of power, but have seen the turtle twice, luckily both times close enough to home. I think on one of those occasions I went at least 3 miles on turtle power. It was really stressful not knowing how much further I could go, and wondering where I could get 200 feet of extension cord to plug into some random person's outlet for an hour.

My car did not behave differently in any way, the lights did not dim, nothing changed. On the dashboard, the charge indicator was flashing and the turtle icon appeared, that's it.

When the power meter hits zero, you are turtling. So yes in a way it works the same where you can still get a few miles - but exactly how much is something I do not accurately know, just that it is more than 3 miles going really slowly on streets with no variance in altitude!
 
carnut1100 said:
Turtle light came on, battery gauge flashing, then as I came up the last hill a couple of hundred metres from home it just lost power and stopped...

Were you at the top of the hill ? Could you coast down it. Would it go into Neutral ?
Just curious in case that ever happens to me
 
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